siRNAs and RNA Interference
RNA interference (RNAi) is a phenomenon involving double-stranded (ds) RNA-dependent gene specific posttranscriptional silencing. Originally, attempts to study this phenomenon and to manipulate mammalian cells experimentally were frustrated by an active, non-specific antiviral defence mechanism which was activated in response to long dsRNA molecules; see Gil et al. 2000, Apoptosis, 5:107-114. Later it was discovered that synthetic duplexes of 21 nucleotide RNAs could mediate gene specific RNAi in mammalian cells, without the stimulation of the generic antiviral defence mechanisms (see Elbashir et al. Nature 2001, 411:494-498 and Caplen et al. Proc Natl Acad Sci 2001, 98:9742-9747). As a result, small interfering RNAs (siRNAs), which are short double-stranded RNAs, have become powerful tools in attempting to understand gene function.
Thus, RNA interference (RNAi) refers to the process of sequence-specific post-transcriptional gene silencing in mammals mediated by small interfering RNAs (siRNAs) (Fire et al, 1998, Nature 391, 806) or microRNAs (miRNAs) (Ambros V. Nature 431:7006, 350-355 (2004); and Bartel D P. Cell. 2004 Jan. 23; 116(2): 281-97 MicroRNAs: genomics, biogenesis, mechanism, and function). The corresponding process in plants is commonly referred to as specific post-transcriptional gene silencing or RNA silencing and is also referred to as quelling in fungi. An siRNA is a double-stranded RNA molecule which down-regulates or silences (prevents) the expression of a gene/mRNA of its endogenous (cellular) counterpart. RNA interference is based on the ability of dsRNA species to enter a specific protein complex, where it is then targeted to the complementary cellular RNA and specifically degrades it. Thus, the RNA interference response features an endonuclease complex containing an siRNA, commonly referred to as an RNA-induced silencing complex (RISC), which mediates cleavage of single-stranded RNA having a sequence complementary to the antisense strand of the siRNA duplex. Cleavage of the target RNA may take place in the middle of the region complementary to the antisense strand of the siRNA duplex (Elbashir et al 2001, Genes Dev., 15, 188). In more detail, longer dsRNAs are digested into short (17-29 bp) dsRNA fragments (also referred to as short inhibitory RNAs—“siRNAs”) by type III RNAses (DICER, DROSHA, etc., Bernstein et al., Nature, 2001, v. 409, p. 363-6; Lee et al., Nature, 2003, 425, p. 415-9). The RISC protein complex recognizes these fragments and complementary mRNA. The whole process is culminated by endonuclease cleavage of target mRNA (McManus&Sharp, Nature Rev Genet, 2002, v. 3, p. 737-47; Paddison &Hannon, Curr Opin Mol Ther. 2003 June; 5(3): 217-24). For information on these terms and proposed mechanisms, see Bernstein E., Denli A M. Hannon G J: 2001 The rest is silence. RNA. I; 7(11): 1509-21; Nishikura K.: 2001 A short primer on RNAi: RNA-directed RNA polymerase acts as a key catalyst. Cell. I 16; 107(4): 415-8 and PCT publication WO 01/36646 (Glover et al).
The selection and synthesis of siRNA corresponding to known genes has been widely reported; see for example Chalk A M, Wahlestedt C, Sonnhammer E L. 2004 Improved and automated prediction of effective siRNA Biochem. Biophys. Res. Commun. June 18; 319(1): 264-74; Sioud M, Leirdal M., 2004, Potential design rules and enzymatic synthesis of siRNAs, Methods Mol Biol.; 252:457-69; Levenkova N, Gu Q, Rux J J. 2004, Gene specific siRNA selector Bioinformatics. I 12; 20(3): 430-2. and Ui-Tei K, Naito Y, Takahashi F, Haraguchi T, Ohki-Hamazaki H, Juni A, Ueda R, Saigo K., Guidelines for the selection of highly effective siRNA sequences for mammalian and chick RNA interference Nucleic Acids Res. 2004 I 9; 32(3):936-48. Se also Liu Y, Braasch D A, Nulf C J, Corey D R. Efficient and isoform-selective inhibition of cellular gene expression by peptide nucleic acids, Biochemistry, 2004 I 24; 43(7):1921-7. See also PCT publications WO 2004/015107 (Atugen) and WO 02/44321 (Tuschl et al), and also Chiu Y L, Rana T M. siRNA function in RNAi: a chemical modification analysis, RNA 2003 September; 9(9):1034-48 and U.S. Pat. Nos. 5,898,031 and 6,107,094 (Crooke) for production of modified/more stable siRNAs.
Several groups have described the development of DNA-based vectors capable of generating siRNA within cells. The method generally involves transcription of short hairpin RNAs that are efficiently processed to form siRNAs within cells. Paddison et al. PNAS 2002, 99:1443-1448; Paddison et al. Genes & Dev 2002, 16:948-958; Sui et al. PNAS 2002, 8:5515-5520; and Brummelkamp et al. Science 2002, 296:550-553. These reports describe methods to generate siRNAs capable of specifically targeting numerous endogenously and exogenously expressed genes.
Several studies have revealed that siRNA therapeutics are effective in vivo in both mammals and in humans. Bitko et al., have shown that specific siRNA molecules directed against the respiratory syncytial virus (RSV) nucleocapsid N gene are effective in treating mice when administered intranasally (Bitko et al., “Inhibition of respiratory viruses by nasally administered siRNA”, Nat. Med. 2005, 11(1):50-55). A review of the use of siRNA in medicine was recently published by Barik S. in J. Mol. Med (2005) 83: 764-773). Furthermore, a phase I clinical study with short siRNA molecule that targets the VEGFR1 receptor for the treatment of Age-Related Macular Degeneration (AMD) has been conducted in human patients. The siRNA drug administered by an intravitreal inter-ocular injection was found effective and safe in 14 patients tested after a maximum of 157 days of follow up (Boston Globe Jan. 21, 2005).
The p53 Gene and Polypeptide
The human p53 gene is a well-known and highly studied gene. The p53 polypeptide plays a key role in cellular stress response mechanisms by converting a variety of different stimuli, for example DNA damaging conditions, such as gamma-irradiation, deregulation of transcription or replication, and oncogene transformation, into cell growth arrest or apoptosis (Gottlieb et al, 1996, Biochem. Biophys. Acta, 1287, p. 77). The p53 polypeptide is essential for the induction of programmed cell death or “apoptosis” as a response to such stimuli.
Most anti-cancer therapies damage or kill also normal cells that contain native p53, causing severe side effects associated with the damage or death of healthy cells. Since such side effects are to a great extent determined by p53-mediated death of normal cells, the temporary suppression of p53 during the acute phase of anti-cancer therapy has been suggested as a therapeutic strategy to avoid these severe toxic events. This was described in U.S. Pat. No. 6,593,353 and in Komarov P G et al, 1999, A chemical inhibitor of p53 that protects mice from the side effects of cancer therapy, Science, 285(5434):1651, 1653. p53 has been shown to be involved in chemotherapy and radiation-induced alopecia. (Botcharev et al, 2000, p53 is essential for Chemotherapy-induced Hair Loss, Cancer Research, 60, 5002-5006).
RTP801
Gene RTP801, was first reported by the assignee of the instant application. U.S. Pat. Nos. 6,455,674, 6,555,667, and 6,740,738, all assigned to the assignee of the instant application, disclose and claim per se the RTP801 polynucleotide and polypeptide, and antibodies directed toward the polypeptide. RTP801 represents a unique gene target for hypoxia-inducible factor-1 (HIF-1) that may regulate hypoxia-induced pathogenesis independent of growth factors such as VEGF.
Pro-Apoptotic Genes.
Pro-apoptotic genes are genes that play a role in apoptotic cell death. A non-limiting list of pro-apoptotic genes includes p53 and RTP801 and also Caspase 1, Caspase 2, Caspase 3, Caspase 4, Caspase 5, Caspase 6, Caspase 7, Caspase 8, Caspase 9, Caspase 10, Caspase 12, Caspase 14, Apaf-1, Nod1, Nod2, Ipaf, DEFCAP, RAIDD, RICK, Bcl10, ASC, TUCAN, ARC, CLARP, FADD, DEDD, DEDD2, Cryopirin, PYC1, Pyrin, TRADD, UNC5a, UNC5b, UNC5c, ZUD, p84N5, LRDD, CDK1, CDK2, CDK4, CDK5, CDK9, PITSLRE A, CHK2, LATS1, Prk, MAP4K1, MAP4K2, STK4, SLK, GSK3alpha, GSK3beta, MEKK1, MAP3K5 (Ask1), MAP3K7, MAP3K8, MAP3K9, MAP3K10, MAP3K11, MAP3K12, DRP-1, MKK6, p38, JNK3, DAPK1, DRAK1, DRAK2, IRAK, RIP, RIP3, RIP5, PKR, IRE1, MSK1, PKCalpha, PKCbeta, PKCdelta, PKCepsilon, PKCeta, PKCmu, PKCtheta, PKCzeta, CAMK2A, HIPK2, LKB1, BTK, c-Src, FYN, Lck, ABL2, ZAP70, TrkA, TrkC, MYLK, FGFR2, EphA2, AATYK, c-Met, RET, PRKAA2, PLA2G2A, SMPD1, SMPD2, SPP1, FAN, PLCG2, IP6K2, PTEN, SHIP, AIF, AMID, Cytochrome c, Smac, HtrA2, TSAP6, DAP-1, FEM-1, DAP-3, Granzyme B, DIO-1, DAXX, CAD, CIDE-A, CIDE-B, Fsp27, Ape1, ERCC2, ERCC3, BAP31, Bit1, AES, Huntingtin, HIP1, hSir2, PHAP1, GADD45b, GADD34, RAD21, MSH6, ADAR, MBD4, WW45, ATM, mTOR, TIP49, diubiquitin/FAT10, FAF1, p193, Scythe/BAT3, Amida, IGFBP-3, TDAG51, MCG10, PACT, p52/RAP, ALG2, ALG3, presenelin-1, PSAP, AIP1/Alix, ES18, mda-7, p14ARF, ANT1, p33ING1, p33ING2, p53AIP1, p53DINP1, MGC35083, NRAGE, GRIM19, lipocalin 2, glycodelin A, NADE, Porimin, STAG1, DAB2, Galectin-7, Galectin-9, SPRC, FLJ21908, WWOX, XK, DKK-1, Fzd1, Fzd2, SARP2, axin 1, RGS3, DVL1, NFkB2, IkBalpha, NF-ATC1, NF-ATC2, NF-ATC4, zf3/ZNF319, Egr1, Egr2, Egr3, Sp1, TIEG, WT1, Zac1, Icaros, ZNF148, ZK1/ZNF443, ZNF274, WIG1, HIVEP1, HIVEP3, Fliz1, ZPR9, GATA3, TR3, PPARG, CSMF, RXRa, RARa, RARb, RARg, T3Ra, ERbeta, VDR, GR/GCCR, p53, p73alpha, p63(human [ta alpha, ta beta, ta gamma, da alpha, da beta, da gamma], 53BP2, ASPP1, E2F1, E2F2, E2F3, HIF1 alpha, TCF4, c-Myc, Max, Mad, MITF, Id2, Id3, Id4, c-Jun, c-Fos, ATF3, NF-IL6, CHOP, NRF1, c-Maf, Bach2, Msx2, Csx, Hoxa5, Ets-1, PU1/Spi1, Ets-2, ELK1, TEL1, c-Myb, TBX5, IRF1, IRF3, IRF4, IRF9, AP-2 alpha, FKHR, FOXO1A, FKHRL1, FOXO3a, AFX1, MLLT7, Tip60, BTG1, AUF1, HNRPD, TIA1, NDG1, PCBP4, MCG10, FXR2, TNFR2, LTbR, CD40, CD27, CD30, 4-1BB, TNFRSF19, XEDAR, Fn14, OPG, DcR3, FAS, TNFR1, WSL-1, p75NTR, DR4, DR5, DR6, EDAR, TNF alpha, FAS ligand, TRAIL, Lymphotoxin alpha, Lymphotoxin beta, 4-1BBL, RANKL, TL1, TWEAK, LIGHT, APRIL, IL-1-alpha, IL-1-beta, IL-18, FGF8, IL-2, IL-21, IL-5, IL-4, IL-6, LIF, IL-12, IL-7, IL-10, IL-19, IL-24, IFN alpha, IFN beta, IFN gamma, M-CSF, prolactin, TLR2, TLR3, TLR4, MyD88, TRIF, RIG-1, CD14, TCR alpha, CD3 gamma, CD8, CD4, CD7, CD19, CD28, CTLA4, SEMA3A, SEMA3B, HLA-A, HLA-B, HLA-L, HLA-DMalpha, CD22, CD33, CALL, DCC, ICAM1, ICAM3, CD66a, PVR, CD47, CD2, Thy-1, SIRPa1, CD5, E-cadherin, ITGAM, ITGAV, CD18, ITGB3, CD9, IgE Fc R beta, CD82, CD81, PERP, CD24, CD69, KLRD1, galectin 1, B4GALT1, C1q alpha, C5R1, MIP1alpha, MIP1beta, RANTES, SDF1, XCL1, CCCKR5, OIAS/OAS1, INDO, MxA, IFI16, AIM2, iNOS, HB-EGF, HGF, MIF, TRAF3, TRAF4, TRAF6, PAR-4, IKKGamma, FIP2, TXBP151, FLASH, TRF1, IEX-1S, Dok1, BLNK, CIN85, Bif-1, HEF1, Vav1, RasGRP1, POSH, Rac1, RhoA, RhoB, RhoC, ALG4, SPP1, TRIP, SIVA, TRABID, TSC-22, BRCA1, BARD1, 53BP1, MDC1, Mdm4, Siah-1, Siah-2, RoRet, TRIM35, PML, RFWD1, DIP1, Socs1, PARC, USP7, CYLD, TP53BP2, CYBA, NOX3, HRK, C1QBP, BNIP3, MAPK8, MAPK14, P2RX7, TRPM2, PARG, CD38, STEAP4, BMP2, GJA1, TYROBP, CTGF, RTN4R, ANXA2, DUOX1, SLC5A1, SLC2A2, AKR1B1, SORD, SLC2A1 and MME.
Chemical-Induced Ototoxicity
The toxic effects of various ototoxic therapeutic drugs on auditory cells and spiral ganglion neurons are often the limiting factor for their therapeutic usefulness. Main ototoxic drugs include the widely used chemotherapeutic agent cisplatin and its analogs, commonly used aminoglycoside antibiotics, e.g. gentamicin, for the treatment of infections caused by gram-negative bacteria, quinine and its analogs, salicylate and its analogs, and loop-diuretics.
For example, antibacterial aminoglycosides such as gentamicins, streptomycins, kanamycins, tobramycins, and the like are known to have serious toxicity, particularly ototoxicity and nephrotoxicity, which reduces the usefulness of such antimicrobial agents (see Goodman and Gilman's The Pharmacological Basis of Therapeutics, 6th ed., A. Goodman Gilman et al., eds; Macmillan Publishing Co., Inc., New York, pp. 1169-71 (1980)). Clearly, ototoxicity is a dose-limiting side-effect of antibiotic administration. From 4 to 15% of patients receiving 1 gram per day for greater than 1 week develop measurable hearing loss, which slowly becomes worse and can lead to complete permanent deafness if treatment continues.
Ototoxicity is also a serious dose-limiting side-effect for cisplatin, a platinum coordination complex, that has proven effective on a variety of human cancers including testicular, ovarian, bladder, and head and neck cancer. Cisplatin (Platinol®) damages auditory and vestibular systems. Salicylates, such as aspirin, are the most commonly used therapeutic drugs for their anti-inflammatory, analgesic, anti-pyretic and anti-thrombotic effects. Unfortunately, they too have ototoxic side effects. They often lead to tinnitus (“ringing in the ears”) and temporary hearing loss. Moreover, if the drug is used at high doses for a prolonged time, the hearing impairment can become persistent and irreversible.
Accordingly, there exists a need for means to prevent, reduce or treat the incidence and/or severity of inner ear disorders and hearing impairments involving inner ear tissue, particularly inner ear hair cells. Of particular interest are those conditions arising as an unwanted side-effect of ototoxic therapeutic drugs including cisplatin and its analogs, aminoglycoside antibiotics, salicylate and its analogs, or loop diuretics. In addition, there exits a need for methods which will allow higher and thus more effective dosing with these ototoxicity-inducing pharmaceutical drugs, while concomitantly preventing or reducing ototoxic effects caused by these drugs. What is needed is a method that provides a safe, effective, and prolonged means for prophylactic or curative treatment of hearing impairments related to inner ear tissue damage, loss, or degeneration, particularly ototoxin-induced and particularly involving inner ear hair cells.
Without being bound by theory, it is believed that cisplatin drugs and other drugs that induce ototoxicity (such as aminoglycoside antibiotics) may induce the ototoxic effects via programmed cell death or apoptosis in inner ear tissue, particularly inner ear hair cells (Zhang et al., Neuroscience 120 (2003) 191-205; Wang et al., J. Neuroscience 23((24):8596-8607). In mammals, auditory hair cells are produced only during embryonic development and do not regenerate if lost during postnatal life, therefore, a loss of hair cells will result in profound and irreversible deafness. Unfortunately, at present, there are no effective therapies to treat the cochlea and reverse this condition. Thus, an effective therapy to prevent cell death of auditory hair cells would be of great therapeutic value.